Aboard the Odyssey, SG-1 undertakes a dangerous mission to the city of Atlantis, deep in the Pegasus galaxy. There, Mitchell and Carter join forces with Dr. Rodney McKay and fly to the nearest black hole, where they deploy a stargate into space and dial another stargate in the Milky Way. That second 'gate is floating beside the Ori's supergate, where Teal'c also waits in a cargo ship to observe the results. Carter plans to detonate a nuclear warhead at the Pegasus galaxy 'gate after it's connected to the Milky Way 'gate. If her theory is correct, the nuke's explosive blast will force the wormhole to leap from its original destination to the next nearest receiving gate — in this case, the supergate. With the supergate thus dialed in — and the black hole sustaining the connection indefinitely — the Ori will be unable to use their massive portal to transport more troops, ships, and supplies to their war against the Milky Way.

Each detail of this incredibly complex operation must be calculated perfectly, so Carter's willing to put up with McKay's prickly exterior if he can help her get the work done. Despite their combined brilliance, however, their first two attempts fail: Teal'c reports that the wormhole fails to jump to the supergate.

Meanwhile, at Atlantis, Daniel and Vala search the city's vast archives for information about Merlin's anti-Ori weapon. To their surprise, however, they find themselves being helped by an unexpected ally: an actual Ascended Ancient, Morgan le Fay. Though she once opposed Merlin's plans, now — faced with the dire threat of the Ori — she wants to help the humans find the weapon. She tells them the locations and the Ancient names — Taoth Vaclarah and Valos Cor — of two planets where Merlin's weapon might be hidden. Ascended law, however, forbids such interference with the human plane of existence, so she's risking terrible punishment by speaking to them at all. Even Daniel's heartfelt pleas might not give her enough courage to say more.

At the black hole, Carter's ambitious plan is not only running out of nuclear warheads, it's running out of time. An Ori ship is closing in on Teal'c's position, and soon the Odyssey is assaulted by the Wraith, the Pegasus galaxy's most dangerous denizens. With both ends of the operation about to be wiped out, Carter, McKay and Mitchell must brave the outer edges of the black hole in order to save their lives.

DAVID HEWLETT	......	Dr. Rodney McKay
JOE FLANIGAN	......	Lt. Col. John Sheppard
TORRI HIGGINSON	......	Dr. Elizabeth Weir
MATTHEW GLAVE	......	Col. Paul Emerson
CHELAH HORSDAL	......	Lt. Womack
DAVID NYKL	......	Dr. Zelenka
Written by	......	Brad Wright
Director	......	Will Waring